Hmm, both are "possible but not implemented yet". The engineering approach that some of our users do is running their own custom monitoring script (checking TCP connections, checking against a dynamic list) on their own infrastructure, and then just use Heii On-Call to monitor (via Inbound Liveness heartbeats / checkins) and alert on (via Manual trigger type) that custom monitoring script. Feel free to email us at support-at-domain so we can try to understand the use case better.